Of the eleven ahupua'a contained within the Ko‘olau-poko District, Kailua, like Kāne‘ohe, was historically among the most important. Early settlers took advantage of the area's rich food, water, and other natural resources. Primarily, however, Kailua was then a kalo-based agricultural area.

Kailua was the home of the ali‘i Kuali‘i in the early 18th century, and presumably had been the seat of the high chiefs of Ko‘olaupoko from very early times. The beach, the bay, and living conditions were and are very attractive. Waimanalo and Kāne‘ohe, both rich farming areas, were neighboring. Access to the northern districts of Ko`olaupoko was easy over the waters of the great indentation in the coast now called Kāne‘ohe Bay, which extends from Kāne‘ohe harbor along the whole Ko‘olaupoko coast, past He‘eia, Kahalu‘u, Ka‘alaea, Waiahole, Waikane, and Hakipu‘u to Kualoa. All these districts were rich in agricultural resources and fishing grounds, but were not attractive from the point of view of residence.

Undoubtedly further reasons for the attractiveness of Kailua as a place of residence for an ali&lsquoi nui with his large entourage were the great natural fishponds, Ka‘elepulu and Kawainui, and the complex of artificial salt-water ponds that are between Kailua and Kane`ohe in the Mōkapu area: Halelou, Nu‘upia, and Kaluapuhi. (1)

Kailua's water resources were developed in pre-contact times, with establishment of lo‘i kalo or taro field terraces, and associated irrigation systems. Such lo‘i kalo were inextricably linked with fishponds (see Hawaiian Fishponds). By late pre-contact times, Hawaiians had converted approximately 250 acres along the inland (mauka) edge of what was then a marsh-fringed lagoon at Kawai Nui, into a productive taro field. A 450-acre inland fishpond (loko wai) was also established at Kawai Nui, and was linked with the drainage system of a similar taro and fishpond complex at nearby Ka‘elepulu. Kawai Nui is the largest fresh-water marsh in the state. It contains a veritable treasure chest of archaeological and geological clues to the watershed's past.

Kailua must formerly have been very rich agriculturally, having one of the most extensive continuous terrace areas on Oahu, extending inland one and a half miles from the margin of Kawainui.... Terraces extended up into the various valleys that run back into the Ko‘olau [mountain]. There were some terraces watered by springs and a small stream from Olomana mountain along the western slope of the ridge that lies southeast of Kawainui..., and another system of terraces was east of the seaward end of the ridge, watered by the stream which joins Kawainui and Ka‘elepulu Ponds. There were also terraces north of the Kawainui Pond, and several terrace areas flanked Ka‘elepulu Pond at the base of the ridge to the eastward. Much former taro land reverted to [marsh] when abandoned....(1)

For a period of about 100 years between 1850 and 1950, the Kailua ahupua‘a was a significant source of commercial agriculture, particularly for rice and sugar, as well as ranching. Activation of MCBH in 1952 (then as Marine Corps Air Station Kaneohe Bay or MCAS), combined with improved commuter routes to Honolulu, hastened Kailua's conversion from agriculture to urban use in the late 1950s. By that time, large areas along the Oneawa flood control channel that were formerly under cultivation had been developed and subdivided. Today, little agriculture remains in what is mostly an urbanized area. However, much of Maunawili Valley still retains a rural character.

The town of Kailua was built on a broad plain of ancient beach and dune sand. One of the town's most prevalent features is Kailua Beach, a long stretch of sandy shore fronting Kailua Bay. Backed by dune ridges and water-soaked sand flats, Kailua Beach averages about 100 ft (30 m) in width, although the shoreline position is highly variable. Due to erosion, particularly at the Lanikai end, beach replenishment has been an issue since the late 1970s.

Kailua's shallow groundwater table is responsible for major flooding that tends to occur during large storm events. The Kawai Nui Flood Control Project, completed in 1966 to move water from Kawai Nui Marsh to Kailua Bay, and the Ka‘elepulu Canal, originally built by early rice farmers to control water flow from the marsh to their pond fields, have eased flooding to some extent, although urbanization and associated creation of impervious, paved surfaces have created localized ponding problems. Kawai Nui Canal, the major outlet for Kawai Nui Marsh, flows at about 10 million gallons per day. This water originates from streams and springs that drain a large area of inland watershed (Maunawili) and about 1.35 mi2 (3.5 km2) of densely inhabited residential lands.

The mouth of Ka‘elepulu Canal, which drains the area known as Enchanted Lake, enters the coast of Kailua Bay at Kailua Beach Park, forming a large, brackish muliwai (a stream mouth isolated from the sea). A sand bar that helps the muliwai form is present during periods of low stream flow in Ka‘elepulu Canal. It is breached for short periods following periodic channel cleaning and by runoff flow diuring major storms.

  Watershed Descriptions on the Web 
     Maunawili Stream
Kawai Nui Marsh
Kawainui Stream
Kailua Bay

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SOURCES: Modified from Marine Corps Base Hawaii - Kaneohe. 1998. Mokapu: Manual for Watershed Health and Water Quality, Sections 3.4
(1) modified from E. S. C. Handy, E. G. Handy, and Mary Pukui. 1972. Native Planters in Old Hawaii. Their Life, Lore, and Environment, Bernice P. Bishop Museum Bulletin 233: p. 457